In this project we seek to clarify and expand the nosology of the hereditary movement disorders, contribute to the understanding of their underlying biochemical basis, determine the most effective treatment for each and suggest guidelines for counseling individuals at risk. General syndromes under study include the dystonias, tic disorders including Tourette syndrome, Huntington's chorea and myoclonus. Approaches include standard epidemiologic and clinical genetic studies together with collaborative efforts in evaluating the role of neurotransmitters such as dopamine, their precursors, and metabolites, and their necessary cofactors. Low levels of biopterin, the hydroxylase cofactor for tyrosine, tryptophan, and phenylalanine in CSF of four patients with familial dystonia suggest a promising area for study.